1. Field of the Invention
The present invention relates to a method of manufacturing a pipe liner bag for use in repairing pipelines.
2. Description of the Related Art
When an underground pipe, such as pipelines and passageways, becomes defective or too old to perform properly, the pipe is repaired and rehabilitated without digging the earth to expose the pipe and disassembling the sections of the pipe. This non-digging method of repairing an underground pipe has been known and practiced commonly in the field of civil engineering. The pipe lining method utilizes a tubular pipe liner bag made of a resin absorbent material impregnated with a hardenable resin, and having the outer surface covered with a highly air-tight plastic film. The tubular pipe liner bag is inserted into a pipe to be repaired by means of a pressurized fluid such that the pipe liner bag is turned inside out as it proceeds deeper in the pipe. Hereinafter, this manner of insertion shall be called "everting". When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the pipe, the everted tubular liner is pressed against the inner wall of the pipe by a pressurized fluid, and the tubular flexible liner is hardened as the hardenable resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag. It is thus possible to line the inner wall of the defective or old pipe with a rigid liner without digging the ground and disassembling the pipe sections.
In the pipe liner bag used in the above-mentioned pipe lining method, the thickness of the material of the pipe liner bag is adjusted in order to ensure a required strength. The adjustment of the thickness is typically made by laminating a plurality of tubular resin absorbent materials to form a multi-layer structure.
For example, when a pipe liner bag is formed of two layers of tubular resin absorbent materials for ensuring a required thickness, a resin absorbent material made of unwoven fabric is first rolled and both ends are joined to form a first layer of tubular resin absorbent material. Then, another strip-like resin absorbent material is surrounded over the first layer of tubular resin absorbent material and both ends are joined to form a second layer of tubular resin absorbent material. Then, the outer surface of the two-layer tubular resin absorbent material is coated with a plastic film. In this way, a pipe liner bag having a desired thickness is manufactured.
A process of coating the outer surface of the tubular resin absorbent material with the plastic film involves the work requiring the most expertise in the method of manufacturing the multi-layer pipe liner bag. However, since this coating is performed on a heavy multi-layer tubular resin absorbent material, there is a problem that the workability is extremely low. Particularly, for manufacturing a large-diameter and thick pipe liner bag, an operation for modifying a large and heavy pipe liner bag deviated from a machining line is hard, and the plastic film covering the outer surface of the pipe liner bag is often scratched during treatments of the pipe liner bag.
In addition, a process of surrounding a strip-like resin absorbent material over the outer periphery of the tubular-formed first resin absorbent material to form a second and subsequent layers of resin absorbent materials also involves hard work, so that a large amount of labor and time is required.